Magento 2 Product – How to Remove Add to Cart from Catalog/Category/View

I see that you are using the Infortis Ultimo theme for your store and have made a lot of customizations to it. This issue is not occuring in the default Ultimo theme so it must be related to your own customizations. The ratings box that you want to remove is in the my_sub_con div class. Try to locate it and remove it.

If we look at this module-catalog\view\frontend\templates\product\list.phtml around line 80 There is function $_product->isSaleable() which then again call to isSalable() function of Magento\Catalog\Model\Product.

There are two events in it catalog_product_is_salable_before and catalog_product_is_salable_after. Depending on your need you can modify it.

I used catalog_product_is_salable_after event to hide Add to Cart button

namespace Namespace\Module\Observer\Frontend;

use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;

class classname implements ObserverInterface
{
    public $request;

    public function __construct(
        \Magento\Framework\App\Request\Http $request
    ) {
        $this->request = $request;
    }

    public function execute(Observer $observer)
    {
        if ($this->request->getFullActionName() == 'catalog_category_view')
        {

            $product = $observer->getEvent()->getProduct();
            $saleble = $observer->getEvent()->getSalable();

            if($product->getTypeId() == 'customProductType')
            {
                $saleble->setIsSalable(false);
                $salable = $product->getStatus() == \Magento\Catalog\Model\Product\Attribute\Source\Status::STATUS_ENABLED;
                if ($salable && $product->hasData('is_salable')) {
                    $salable = $product->getData('is_salable');
                }
                $product->setIsSaleable($salable);                        
            }
        }
        return $this;
    }
}

Though this will add In Stock or Out of Stock in place of Add to Cart.